In the U.S., nearly 1.4 million older persons survive an episode of critical illness every year. This number is expected to grow with the aging of our population and advances in critical care medicine leading to improved ICU survivorship. Disability in carrying out activities essential to independent living is frequently seen in older IU survivors. This finding has significant clinical and public health importance because disability is associated with increased mortality, institutionalization, and greater use of formal and informal home services. To inform the development of evidence-based interventions directed at improving functional outcomes, a comprehensive understanding of the epidemiology of disability among older persons who experience critical illness is essential. This evaluation must consider the impact of preexisting frailty and cognitive impairment, two vulnerability factors that are known to increase adverse outcomes in older persons without critical illness. Currently, relatively little is known about the effect of preexisting frailty and cognitive impairment on the type and burden of disability among older survivors of critical illness. Additionally, while hospitalization-associated disability has been well described, the burden of disability after critial illness relative to that observed after other hospitalizations has not been previously evaluated. The overall objective of this proposal is to evaluate the type and burden of disability among older survivors of critical illness, with special attention to the role of preexisting vulnerabilit factors and to quantifying the relative magnitude of disability after critical illness to that obseved after other hospitalizations. We will achieve this objective with the following three aims: (1) Among older persons with critical illness, to evaluate the effect of preexisting frailty on new or worsening post-ICU disability (in basic, instrumental, and mobility activities) and with long-term nursing home admissions, relative to critically ill older persons without frailty; (2) To evaluate he independent and combined effects of preexisting cognitive impairment and frailty on post-ICU outcomes in critically ill older persons, including mortality, disability, and long-term nursing hoe admissions; and (3) To evaluate the association of critical illness with new or worsening disability and with long-term nursing home admissions, relative to a matched group of older persons hospitalized with a non-critical illness, while accounting for frailty and cognitive impairment. By using high quality data from a unique longitudinal study of older persons that includes monthly assessments of functional status and comprehensive assessments every 18 months over the course of 15+ years, we have assembled a sizeable and growing cohort of critically ill older persons who have been carefully phenotyped both before and after their critica illness. The results of our analyses will be used to develop targeted interventions to reduce disability and optimize functional outcomes in older survivors of critical illness, which is the log-term goal of the candidate and proposed research.